A light pen which works in conjunction with an image sensor array to allow the sensor array to distinguish between a finger touch and touch by the light pen. The light pen is arranged to pass through a laser curtain or other light source undetected by the image sensor.
1. A system for determining a position on a surface, comprising:
a light source arrangement generating at least one incident light beam;
a pointing device comprising:
a body portion comprising a portion including light absorbent material;
a proximal portion at an extent of the pointing device configured to be proximal to the surface; and
a light emitting unit for radiating light when actuated by contact between the proximal portion and the surface; and
a light sensor arrangement configured to sense reflected light from objects interrupting the at least one incidental light beam and the radiated light from the light emitting unit, wherein an output from the light sensor arrangement is processed to determine the position of detected objects on the surface, and the light absorbent material of the body portion prevents light to reflect back to the light sensor arrangement;
wherein the proximal portion of the pointing device is made of an admissive material that admits a substantial portion of the incident light from the light source arrangement to avoid detection of the pointing device passing through the incident light from the light source arrangement without contact of the pointing device contacting the surface, and the light emitting unit is detected by the light sensor arrangement upon contact of the pointing device with the surface.
2. The system of claim 1 , wherein the portion of the incident light admitted by the proximal portion of the pointing device has a cumulative power that exceeds 50 percent of the power of the incident light.
3. The system of claim 2 , wherein the portion of the incident light admitted by the proximal portion of the pointing device has a cumulative power in the range from 90 percent to 95 percent of the power of the incident light.
4. The system of claim 1 , further comprising:
a projector system configured to project an image onto the surface, wherein the determined position of the detected objects is represented as a graphical element of the projected image.
5. The system of claim 1 , wherein the at least one incidental light beam is a collimated beam.
6. The system of claim 1 , wherein the at least one incidental light beam is a beam of coherent light.
7. The system of claim 1 , wherein the at least one incidental light beam comprises light in the near infrared portion of the electromagnetic spectrum.
8. A pointing device for indicating a position on a surface to a surface tracking system, the surface tracking system including a light source arrangement and a light sensor arrangement, the pointing device comprising:
a body portion comprising a proximate housing section including light absorbent material that prevents light to reflect back to the light sensor arrangement;
a proximal portion at an extent of the pointing device configured to be proximal to the surface; and
a light emitting unit for radiating light only when actuated by contact between the proximal portion and the surface;
wherein the proximal portion is made of an admissive material that admits a substantial portion of the incident light from the light source arrangement to avoid detection by the light sensor arrangement for the pointing device passing through the incident light from the light source arrangement, and the light emitting unit is detected by the light sensor arrangement upon contact of the pointing device with the surface.
9. The pointing device of claim 8 , wherein the proximal portion includes a pen tip section and the proximal housing section.
10. The pointing device of claim 9 , wherein the pen tip section is configured to contact with the surface with a two-dimensional contact footprint.
11. The pointing device of claim 9 , wherein the light absorbent material is manufactured of an IR-absorbent material.
12. The pointing device of claim 9 , wherein the light absorbent material is manufactured of an IR-transparent material.
13. The pointing device of claim 9 , wherein the pen tip section is manufactured of an IR-absorbent material.
14. The pointing device of claim 9 , wherein the pen tip section is manufactured of an IR-transparent material.